Japanese encephalitis

**Definition:** A disease of the brain, caused by an infection with flavivirus. This disease is characterised by fever, headache, meningism, hyperexcitability, or decreased consciousness. This disease may also present with neurological signs such as cranial nerve palsies, tremor and ataxia, parkinsonism, or upper limb paralysis. Transmission is through the bite of an infected mosquito. Confirmation is by identification of flavivirus in a serum sample or cerebrospinal fluid.

**Long definition:** Japanese encephalitis is an arboviral disease (a disease due to a virus transmitted by an arthropod) caused by a flavivirus spread by wild birds, amplified by domestic pigs, and transmitted to humans mainly by a mosquito of the genus Culex. Infected individuals present with signs ranging from moderate with a headache and low-grade fever to more severe infection with high fever, meningeal syndrome (neck stiffness, vomiting), disorientation and sometimes tremors or coma. The disease, when it is symptomatic, can leave neurological sequelae and leads to death in 25 to 30% of the cases.